Silicon carbide (SiC) is a third-generation semiconductor material. With its excellent physical properties such as large forbidden band width, high breakdown electric field, high electron mobility and high thermal conductivity, it is particularly suitable for the preparation of power electronic devices. SiC MOSFETs are the most concerned power electronic devices. Compared with Si MOSFETs, SiC MOSFETs which have low conduction loss, fast switching rate and high temperature tolerance are especially suitable for power switching applications. How to reduce the defects at the gate oxide of the SiC MOSFETs is still the focus of current research.
Since SiC is a compound semiconductor capable of thermally growing SiO2, it is possible to prepare a device structure similar to Si MOS. However, the thermo-oxidation of SiC requires a higher temperature than Si, for example, up to 1300 ° C. Currently, the thermo-oxidation of SiC mainly employs an electric resistance heating furnace in which oxygen molecules reacts with SiC at a high temperature to generate SiO2. The reaction process is performed in thermal equilibrium conditions, resulting in degradation of interface quality such as interface carbon cluster residue, formation of defects such as Si-O-C bonding, dangling bonding of C, oxygen vacancies etc., as shown in FIG. 1. The presence of carbon clusters may form defect centers at the interface, reducing the carrier mobility and the output performance of SiC MOSFETs. In addition, high temperature oxidation may also cause interface damage and reduce oxidation efficiency.
Therefore, an efficient gate oxidation process with low interface state is the key to ensure the reliable operation of SiC MOSFETs. In recent years, a method of oxidizing SiC by plasma at a low temperature has been proposed to improve the interface quality. However, the method has low oxidation efficiency, and requires more oxidation time to obtain a thick gate oxide. In addition, in the oxidation process, SiC and SiO2 are still in a thermodynamic equilibrium state at the interface between SiC and SiO2, resulting in an unsatisfactory interface quality.